Swinging finder mounting



Aug. 27, 1935. G A, M.THE. 2,012,514

SWINGING FINDER MOUNTING Filed Oct. 16, 1933 2 Sheets-Sheet l 17H/enfer CforyeA JY. Mik/26M.

v V927 95 @i Aug. 27, 1935. G. A. MITCHELL 2,012,514

` SWINGING FINDER MOUNTING Filed Oct. 16, 1933 2 Sheets-Sheet 2 J7 f x Y 2- 26 @arzzey Patented Aug. 27, 1935 UNITED STATES SWINGING FINDER MOUNTING George A. Mitchell, Beverly Bills. Calif to Mitchell Camera Corporation,

wood, Calif., a corporation of Application October 16, 1938, Serial Na 893,738

SCIaiml.

'Ihis invention relates generally to view finding instruments as used on motion picture cameras, and more particularly to focusing means for such view ndlng instruments.

The view nnder of a motion picture camera is ordinarily arranged to one side of the camera, and has a vertical mounting enabling it to be swung in a horizontal plane for parallax adjustment, or in other words to bring its ileld of view into coincidence with that on which the camera lens is focused. 'Ihe finder is equipped with a focusing objective, and it is necessary, each time the camera lens is focused on an object at a different distance from the camera, to swing the finder to correct for parallax and also to readjust the focus of the finder objective.

It is an object of the present invention to provide means operative to focus the nnder objective by virtue of the swinging movement of the finder body in making the parallax adjustment.

It is a mathematically demonstrable fact that 4the distance the finder lens must be moved to tion that the finder objective is automatically l moved substantially proportionallyto the tangent of the angle of swing of the finder body as the finder is swung on its pivotal mounting to correct for parallax. Y

The invention will be best understood from the following detailed description of the present pre- .'ferred embodiment thereof, reference for this purpose being had to the accompanying draw'- ings, in which:

Fig. 1 is a side elevation showing a conventional motion picture camera equipped with a view finder; Y

Fig. 2 is a plan view looking down on the view finder shown in Fig. 1 and also showing a portion of the camera;

Fig. 3is adetailedview takenasindioatedby broken lines 3-3 of Fig. l and showing the finder lens focusing mechanism;

Fig. 4 is a view somewhat similar to Fig. 3, but showing the parts in elevation rather than in section, with the gear housing cover plate removed. andalsosliowing theilnderswungtoanangle different from that shown in Rg. 3:

ll'ig.5isaverticallongltudinalsectlonofthe finder taken as indicated by line i-l of Fig. 2:

Fig. 6 is a section taken as indicated by broken line 6-6 of Fig. 3;

Fig. 7 is an enlarged detail taken from Fig. 6;

Fig. 8 is a plan detail of a portion of the finder and mounting showing the nder swung out to 5 inoperative positio and Fig. 9 is a view taken in the direction of line l-I of Fig. 8.

In the drawings there is shown at Ill a conventional motion picture camera comprising base I I, l head l2 risingI from the front end of said base and carrying photographic objective I3, camera box It supported on base Il to the rear of head I2, and film magazine I mounted on box I4. Within box Il is the usual exposure aperture plate and intermittent mechanism for moving the nlm past said plate, these parts not being illustrated since they may be of any conventional design. Focusing tube I1 is mounted on the side of the camera box and extends along one` side thereof to terminate back of a bracket Il extending laterally from camera head I2. Said bracket I8 supports the view finder instrument, designated generally by numeral 20. The use of thefocusing tube in the type of camera illwtrated is well understood and will require no explanation here.

As indicated in the drawings, a view nder carrying bracket, 2| is ntted into stationary bracket Il by means of a, vertical dove-tail way 22. A clamping device, indicated at 23, is provided to lock bracket 2l rigidly to bracket It. Bracket 2l extends outwardly and forwardly from bracket Il, as at the angle shown in the` plan views of the device, and is shaped at its v forward end to provide a yoke which receives a view finder mounting boss 25, a pivot pin 2i extending downwardly through the yoke arms and boss 2i (see Fig. 6). The view nnder swings for its parallax adjustment movement on this pivot pin il. Boss 2l is formed on one side and at 40 theforwardendofaheadcastingll of the finder.

Theforwardendotsaidcastinglhasabore I4 which slidably receives and serves as a bearing for the tubular rearward extension 35 of the 45 forwardly and rearwardly movable view finder objective moimting 8C. The objective combination. designated at I'I, is preferably an erecting combination giving an image which is right side up and correct as for right and left, such a combinati being described in my Reissue Patent No. 17,995, entitled "Erecting nnder."

Casting 3l is substantially rectangular in transverse cross section, comprising top wall 3i,

lbottom1|rall,andsidewalls and42which ss diverge rearwardly, as shown. Secured to the rear end of casting 38, as by screws 43, are upper and lower view nder casing walls and 45, respectively, and side walls 46, which latter diverge rearwardly for a distance in continuation of the side walls of casting 38, and are then parallel to each other, as clearly shown in the drawings. The finder casing walls form with casting 38 a light conduit from objective combination 31 to the rear open end of the instrument. The casing carries suitable optical elements, as a collector lens 48 having a ground glass surface 49 at the proper distance back of objective 31, and a second collector lens 58 back of-lens 48.

Objective mounting 36 has, above and below tubular extension 34, rearwardly extending bosses 52 and 53, respectively, into which are -rigidly set parallel rearwardly extending guide rods 54 and 55, respectively. These guide rods extend through slide bearings 56 and 51 formed on the top and bottom walls 39 and 48 of casting 38. with reference to finder head 38 is limited by engagement of bosses 52 and 53 with the forward ends of bearings 56 and 51, while forward movement of mounting 36 is limitedby engagement of a head 59 on the rear end of upper rod 54 with the rear end of bearing 56.

Slide bearing 56is formed, on its side next the camera, with a vertical face 68, and mounted on finder top wall 39 in engagement with said 'face 60 is a housing 6| for certain automatic focusing gearing to be described. 'I'his housing v6| is made up of bottom 63 resting on wall 39, front wall .64 flush with the front end of finder. head casting 38, a rear wall 65 and angular side wall 66 which merges with arcuate wall 61 joining it to wall 64. The housing is closed by a ing walls 64 and 65 and then screwthreaded into finder wall 39.

Mounted in suitable bearings in lower housing wall 63 and housing top plate' 69 is a verticalv gear shaft 88. This shaft is located adjacent the aforementioned vertical face 68 of slide bearing 56, and has keyed thereon a gear 8| which extends through an aperture 82 in bearing member 56 to engage rack teeth 84 cuton the adjacent surface of rod 54. It will be evident that rotation of shaft 88 willl cause gear -8l to move rod 54 longitudinally in bearing 56, and willconsequently move objective mounting 36 forwardly or rearwardly with reference to the finder body. Such rotation of shaft 88 is derived from swinging of the ilnder body on itspivot mounting pin 26, as now to be described.

Shaft 88 has formed thereon, directly above gear 8|, a smallergear 86. The latter gear is engaged by a gear segment 81, which is fastened, as by rivets 88, on an arm 89 pivoted coaxially with nder mounting pivot pin 26. The pivot axis of arm`89 is also the axis of gear segment 81, so that gear segment 81 is coaxial with the pivot of the nder mounting. Thus, as clearly shown in Fig. 7, arm 89 has a hub 98 which is taken within arcuate housing wall 61 and is rotatable on a stub shaft 92 which is mounted in housing 6| so as to be coaxial with pivot pin 26. For instance, shaft 92 may have reduced Rearward movement of lens mounting 38- ends 93 received in bores 94 in the lower and upper walls 63 and 69 of the housing, and may be secured in place by means of flat headed screws 95 in the manner clearly shown in Fig. 7.

Arm 89 that carries gear segment 81 has a rearward extension 91 projecting rearwardly from housing 6| through aperture 96, and said extension has in its end an open ended slot 98 adapted to receive the shank of clamping screw 99 screwthreaded into the apex end of a substantially triangular plate |88 mounted, as by means of screws |8 on the upper edge of bracket 2| and extending outwardly substantially at right angles thereto. finder body is swung until slot 98 engages the shank of screw 99, and screw 99 is then set up tightly. n win be evident that this peranon locks arm extension 91, and consequently gear segment 81, rigid with brackets 2| and I8, and therefore sets gear segment 81 rigid with the camera.

Fig. 2 in full lines and Fig. 3 show the finder body locked by screw 99 in the operative position mentioned above, and show the finder body swung to a position where its longitudinally center line is approximately parallel to the optical axis O-O of the camera. This is the position for long distance or infinity focus of the camera and finder objectives, and it will be observed that in this posiy tion the finder objective mounting 36 is in its extreme. rearward position with reference to the finder. When the camera objective is then moved to focus on a close-up object, for instance, it becomes necessary to correct for parallax by swinging the view nder until its optical axis or center line intersects that of the camera at said object. Fig. 2 in dotted lines and Fig. 4 show the finder so swung to bring its field of view into coincidence with the close-up view on which the camera objective is now assumed to be focused. I

In so moving from the position of Fig. 3 to that of Fig. 4, gear 86 moves forwardly in an arc about the axis of finder pivot 26 as a center, and in so doing rolls on stationary gear 81, whose center is coaxial with pivot 26. Shaft 88 is accordingly A tive always focused at the distance of the intersection of the vfinder and camera optical axis, to move the finder objective longitudinally with reference to the finder body by an amount proportional to the tangent of the angle throughl which the finder is swung.- It will be evident from a considerationof Figs. 3 and 4 that my mechanism is designed to maintain this tangent relation for all practical purposes. The movement of rod 54 'and objective mounting 36 is proportional to the angle of rotation of gear 8| on shaft 88, and therefore, to the travel of gear 86 on gear 81, which, is obviously proportional to the angle of swing of the finder about its pivot mounting. Within the limits of the comparatively small angle of swing made by the finder, the angle is nearly equal to its tangent, and the longitudinal focusing movement of the nder objective mounting is therefore substantially proportional to the tangent of `the angle of finder swing. Whatever small differences there are between the angle or In operative position the finder swing and its tangent are not sumcient to materially affect the focus of the finder objective.

The gear ratios of the focusing m are properly `:hosen 'so that, starting for` instance with a position wherein the line of the finder is swung inwardly to view a close-up object on which the camera is focused and wherein the finder objective is in a position such as to cast a sharp image on the finder ground glass surface Il.

The yinoperative nder position shown in Fig. 8,

with clamping screw 99 loosened and the finder swung away from the camera, is utilized when it is desired to swing down the camera door Ila, (on which focusing tube l 1 is carried) to gain access to the camera interior.

It will kbe understood that the drawings and' description are merely illustrative of and not restrictive on the broader claims appended hereto, for various changes in design, structure and arrangement may be made without departing from the spirit and scope of said claims.

, I claim:

l. In combination with a camera having a photographic objective, a view iinder comprising a finder body having a vertical pivot mounting on the camera to one side of the optical axis of the camera objective, an objective mounted for rela- `tive longitudinal focusing movement on the view finder body, a gear non-rotatably xed with reference to the camera and having its axis concentric with the axis of the pivot mounting of the finder body, and gear means on the finder body meshing with said fixed gear and adapted to move with relation to and be driven by said fixed gear by virtue of swinging of the view nder on its pivot mountng,'said gear means operatively connected with the finder objective to cause longitudinal focusing movement thereof on the nder body when said finder body is so swung on its pivot mounting. A

2. In combination with a camera having a photographic objective, a view linder comprising a finder body having a vetrical pivot ,mounting on the camera to one side of the optical axis of the camera objective, an objective mounted for relative longitudinal focusing movement on the view finder body, a gear non-rotatably xed with reference to the camera and having its axis concentric with the axis of the pivot mounting of the finder body, a rotatablegear on the nder body meshing with said fixed gear and adapted to move with relation to and be driven by said ilxed gear by `virtue of swinging of the View nder on its pivot mounting, and means adapted to be operated by said rotatable gear to cause longitudinal focusing movement of said iinder obective when the iinder body is so swung on its pivot mounting.

3. In combination with a camera having a photographic objective, a view finder comprising a finder body having a vertical pivot' mounting-on the camera to oneside of the optical axis of the camera objective, an objective mounted for relative longitudinal focusing movement on the view nder body, a gear non-rotatably fixed with reference to the camera and having its axis concentric with the axis of the pivot mounting of the nder body, a rotatable gear on the nder body meshing with said fixed gear and adapted to move with relation to and be driven by said nxed gear by virtue of swinging of the view finder on its pivot mounting, and means adapted to be operated by said rotatable gear including a rack gear connected to the finder objective to cause longitudinal focusing movement of said finder objective when the finder body is so swung on its pivot mounting.

4. In vcombination with a camera having a photographic objective, a view iinder comprising a nder body having a vertical pivot mounting on the camera to one side ofthe optical axis of the camera objective, a view iinder objective mounting mounted for relative longitudinal focusing movement on the view iinder body, a longitudinally extending rack gear mounted on said objective mounting, a gear non-rotatably nxed with reference to the camera and having its axis concentric with the axis of the pivot mounting of the finder body, and a rotatable gear on the finder body meshing with said fixed gear and adapted to move with relation Ato and be driven by saiclY fixed gear by virtue of swinging ofthe view finder on its pivot mounting, said rotatable gearbeing geared to said rack gear, whereby swinging of the finder body on its pivot mounting causes corelated longitudinal focusing movement of the finder objective mounting. l

5. In combination with a camera having a photographic objective, a view finder comprising a finder body having a vertical pivot mounting on the camera to one side of the optical axis of the camera objective, a view finder objective mountingmounted for relative longitudinal focusing movement on the view finder bocLv, a longitudinally extending rack gear mounted on said objective mounting, a gear non-rotatably fixed with reference to the camera and having its axisconcentric with the axis of the pivot mounting of the finder body, a vertical shaft rotatably mounted on the nder body, a gear on said shaft meshing with said fixed gear, and another gear on said shaft meshing with said rack gear, all in such manner that swinging of the finder body on its pivot mounting causes co-related longitudinal focusing movement of the finder objective mounting.

6. In combination with a camera having a photographic objective, a View finder comprising a finder body having a vertical pivot mounting on the camera to one side of the optical axis of the camera'objective, an objective mounted for relative longitudinal focusing movement on the view iinder body, a gear rotatably mounted on the view finder with its axis concentric with the axis of the pivot mounting of the nder body, means for xing said gear against rotation with reference to the camera, a rotatable gear on the finder body meshing with said nrst mentioned f `a finder body having a vertical pivot mounting ori the camera to one side of the optical axis of the camera objective, an objective mounted for relative longitudinal focusing movement on the view nder body, a gear rotatably mounted on the view nder with its axis concentric with the axis of the pivot mounting of the iinder body, a rigid arm on said gear adapted to be detachably connected with the camera to x said gear against rotation with reference to the camera, a rotatable gear on the nder body meshing with said rst mentioned gear, and means adapted to be operated by said last mentioned rotatable gear operatively connected with the nder objective to cause longitudinal focusing movement of said nder objective when the nder body is swung on its pivot mounting.

8. In combination with a camera having a photographic objective, a view finder comprising a nder body havinga vertical pvot mounting on the camera to one side of theopticai axis of the camera objective, an objective mounted for relative longitudinal focusing movement on the view nder body, gear means on the nder body operatively connected with the finder objective, and

a gear non-rotatably fixed with reference to thel camera meshing with said gear means and adapted to drive said gear means to cause longitudinal focusing movement of the nder objective on the finder body by virtue of swinging of the finder body on its pivot mounting with reference to the camera and said fixed non-rotatable gear.

GEORGE A. MITCHELL. 1s 

